This invention relates to a wood chipping machine that utilizes most of the available and unused internal energy of the machine needed to generate chips of a size that they can be further reduced to wood flour in a single low energy cutting and hammering operation. This reduction to wood flour was historically accomplished by chipping logs or wood scraps into chips having a ¾″ length/width or less and then collecting these chips and hammering them into wood flour in a high horsepower, energy inefficient hammer mill. Hammering whole logs and large chips directly into powder has also been attempted but has proven to be extremely inefficient and results in an extremely low production rate.
Typically disc type chippers having sufficiently large enough production rates suitable for use in economic industrial processes, utilize relatively large diameter discs which are generally in the 72″ (1.8 M) range. Depending on the process involved, between 10 and 40 knives are used to obtain an adequate output rate when the disc is rotated at rim speeds of between 9,200 and 12,000 feet per minute (2800-3600 M/min). Accordingly, these machines require a good deal of energy, a high percentage of which is not consumed or utilized in the chipping process but is discharged from the machine with the chips largely in the form of heat.